wps checksum tool

wps_checksum.c

#include <stdio.h>

unsigned int wps_pin_checksum(unsigned int pin);

int main(int argc, char *argv[])
{
	int pin;
	if ((argc == 2 && sscanf(argv[1], "%i", &pin)) || fscanf(stdin, "%i", &pin))
	{
		if (pin > 9999999)
		{
			goto error;
		}
		printf("%07d%d\n", pin, wps_pin_checksum(pin));
		return 0;
	}
	else
	{
		goto error;
	}
	error:
	{
		fprintf(stderr, "Invalid WPS Pin.\n");
		return -1;
	}
}


/**
 * wps_pin_checksum - Compute PIN checksum
 * @pin: Seven digit PIN (i.e., eight digit PIN without the checksum digit)
 * Returns: Checksum digit
 */
unsigned int wps_pin_checksum(unsigned int pin)
{
	unsigned int accum = 0;
	while (pin) {
		accum += 3 * (pin % 10);
		pin /= 10;
		accum += pin % 10;
		pin /= 10;
	}

	return (10 - accum % 10) % 10;
}